I get that very occasionally, it might be useful to split targets, but imo that's so rare that it's not worth the pile of added control complexity and dev time.
For example, say you've got two carriers with 3 bays each, and you want 3 talons and 3 bombers. Is it ever really better to split the talons across multiple carriers? You pretty much always want them to focus on a single target, and likewise with the bombers. Plus if you have one strike-dedicated carrier, then you can mix in heavy fighters there and have them coordinate.
With a 6-bay carrier, the benefit of specializing on a role is even bigger; more bombers means progressively more and more ordnance getting through. I.E. 2 wings worth of bombers may get shut down entirely, while 4 wings may get half of the ordnance through - the increase in effectiveness is nonlinear with the number of wings. Likewise with interceptors, a few wings may be overwhelmed by PD, while more wings will be beyond the ability of PD to keep up with.
The game *does* suggest a mix, it's just that some things mix well (i.e. bombers + heavy fighters, or interceptors + other fast fighters) and some really don't (i.e. bombers + interceptors).
Target-splitting sounds good on paper but I really don't think it'd be all that useful in practice. Something like an Astral splitting a large number of interceptor wings between multiple targets is probably the most compelling potential use case... but are you *really* going to deploy an Astral just to get 6 bays of interceptors on the field? Three Drovers or Condors do the job more cheaply; the real strength of the Astral is the ability to specialize using 6 wings.